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Populate Ephemeral KeyId #43

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db5e57a
abstract out blake2
jazzz Dec 17, 2025
917c97e
Populate ephemeral key id
jazzz Dec 17, 2025
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21 changes: 13 additions & 8 deletions src/chat/client.nim
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Original file line number Diff line number Diff line change
Expand Up @@ -50,7 +50,7 @@ type KeyEntry* = object
type Client* = ref object
ident: Identity
ds*: WakuClient
keyStore: Table[string, KeyEntry] # Keyed by HexEncoded Public Key
keyStore: Table[RemoteKeyIdentifier, seq[KeyEntry]]
conversations: Table[string, Conversation] # Keyed by conversation ID
inboundQueue: QueueRef
isRunning: bool
Expand All @@ -77,7 +77,7 @@ proc newClient*(cfg: WakuConfig, ident: Identity): Client {.raises: [IOError,
var q = QueueRef(queue: newAsyncQueue[ChatPayload](10))
var c = Client(ident: ident,
ds: waku,
keyStore: initTable[string, KeyEntry](),
keyStore: initTable[RemoteKeyIdentifier, seq[KeyEntry]](),
conversations: initTable[string, Conversation](),
inboundQueue: q,
isRunning: false,
Expand Down Expand Up @@ -150,18 +150,23 @@ proc notifyDeliveryAck(client: Client, convo: Conversation,
# Functional
#################################################

proc cacheInviteKey(self: var Client, key: PrivateKey) =

let rki_ephemeral = generateRemoteKeyIdentifier(key.getPublicKey())

self.keyStore[rki_ephemeral] = @[KeyEntry(
keyType: "ephemeral",
privateKey: key,
timestamp: getCurrentTimestamp()
)]

proc createIntroBundle*(self: var Client): IntroBundle =
## Generates an IntroBundle for the client, which includes
## the required information to send a message.

# Create Ephemeral keypair, save it in the key store
let ephemeralKey = generateKey()

self.keyStore[ephemeralKey.getPublicKey().bytes().bytesToHex()] = KeyEntry(
keyType: "ephemeral",
privateKey: ephemeralKey,
timestamp: getCurrentTimestamp()
)
self.cacheInviteKey(ephemeralKey)

result = IntroBundle(
ident: @(self.ident.getPubkey().bytes()),
Expand Down
6 changes: 2 additions & 4 deletions src/chat/conversations/private_v1.nim
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Original file line number Diff line number Diff line change
@@ -1,5 +1,3 @@

import blake2
import chronicles
import chronos
import sds
Expand Down Expand Up @@ -75,15 +73,15 @@ proc getConvoIdRaw(participants: seq[PublicKey],
addrs.sort()
addrs.add(discriminator)
let raw = addrs.join("|")
return utils.hash_func(raw)
return utils.hash_func_str(16, raw)

proc getConvoId*(self: PrivateV1): string =
return getConvoIdRaw(@[self.owner.getPubkey(), self.participant], self.discriminator)


proc calcMsgId(self: PrivateV1, msgBytes: seq[byte]): string =
let s = fmt"{self.getConvoId()}|{msgBytes}"
result = getBlake2b(s, 16, "")
result = utils.hash_func_str(16, s)


proc encrypt*(convo: PrivateV1, plaintext: var seq[byte]): EncryptedPayload =
Expand Down
17 changes: 13 additions & 4 deletions src/chat/crypto.nim
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Original file line number Diff line number Diff line change
@@ -1,11 +1,13 @@
import proto_types

import strformat
import crypto/ecdh
import std/[sysrand]
import results
import sequtils
import std/[endians,sysrand]
import strformat
import types
import utils

import proto_types

export PublicKey, PrivateKey, bytes, createRandomKey, loadPrivateKeyFromBytes, loadPublicKeyFromBytes,
getPublicKey, Dh, Result, get_addr, `$`

Expand Down Expand Up @@ -33,3 +35,10 @@ proc toHex*(key: PublicKey): string =
proc `$`*(key: PublicKey): string =
let byteStr = toHex(key)
fmt"{byteStr[0..3]}..{byteStr[^4 .. ^1]}"

proc generateRemoteKeyIdentifier*(publicKey: PublicKey): RemoteKeyIdentifier =
let bytes = cast[seq[byte]]("WAP") & publicKey.bytes().toSeq()
let hash = utils.hash_func_bytes(4,bytes)
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@kaichaosun kaichaosun Dec 17, 2025

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My AI friend tells me that the collision seems high,

With a 4-byte (32-bit) hash, collisions are extremely easy to find.

There are only 2³² ≈ 4.29 billion possible distinct hash outputs.
By the birthday paradox, you only need about 2¹⁶ ≈ 65,536 different inputs to have a ~50% chance of finding at least one collision.
With around 77,000 to 100,000 random inputs, the probability of a collision becomes virtually certain (>99%).

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@jazzz jazzz Dec 17, 2025

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Collisions are not really a concern here.

  • The identifier is scoped to the ephemeral key set of a single user. The expected number of keys over a clients lifetime is expected to be ~2^11 = 2048 keys - one for each Introduction sent (0.05%).
  • These keys are deleted after they are used, which reduces the number of keys active at a single moment
  • The result of a collision is clients would check all keys in the index
  • The public key is not considered Secret/confidential

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@kaichaosun kaichaosun Dec 17, 2025 •
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It seems an increased counter could achieve similar goal as the boundary is clear, not sure if it's a good idea to use it here.
Also, after a quick search in the code, I don't see there is places using keyStore after set, is it not implemented yet?

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@jazzz jazzz Dec 17, 2025 •
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is it not implemented yet?

Requires the Noise Protocol integration into Inbox. This change integrates the keyId into the invite, and the follow up will handle keyManagement

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@jazzz jazzz Dec 17, 2025 •
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It seems an increased counter could achieve similar goal as the boundary is clear

I generally like this idea, as it saves some more bytes. However it would leak how many invites a given contact has created. I'd have to check to see how that fits with our privacy model.


var result: uint32
littleEndian32(addr result, unsafeAddr hash[0])
2 changes: 1 addition & 1 deletion src/chat/crypto/ecdh.nim
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Expand Up @@ -15,7 +15,7 @@ proc bytes*(key: PublicKey): array[Curve25519KeySize, byte] =

proc get_addr*(pubkey: PublicKey): string =
# TODO: Needs Spec
result = hash_func(pubkey.bytes().bytesToHex())
result = hash_func_str(6,pubkey.bytes().bytesToHex())


proc bytes*(key: PrivateKey): Curve25519Key =
Expand Down
6 changes: 3 additions & 3 deletions src/chat/inbox.nim
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Expand Up @@ -86,14 +86,14 @@ proc sendFrame(ds: WakuClient, remote: PublicKey, frame: InboxV1Frame ): Future[
proc newPrivateInvite(initator_static: PublicKey,
initator_ephemeral: PublicKey,
recipient_static: PublicKey,
recipient_ephemeral: uint32,
recipient_ephemeral: PublicKey,
payload: EncryptedPayload) : InboxV1Frame =

let invite = InvitePrivateV1(
initiator: @(initator_static.bytes()),
initiatorEphemeral: @(initator_ephemeral.bytes()),
participant: @(recipient_static.bytes()),
participantEphemeralId: 0,
participantEphemeralId: cast[int32](generateRemoteKeyIdentifier(recipient_ephemeral)),
discriminator: "",
initial_message: payload
)
Expand All @@ -115,7 +115,7 @@ proc inviteToPrivateConversation*(self: Inbox, ds: Wakuclient, remote_static: Pu
result = convo

# # Build Invite
let frame = newPrivateInvite(self.identity.getPubkey(), local_ephemeral.getPublicKey(), remote_static, 0, encPayload)
let frame = newPrivateInvite(self.identity.getPubkey(), local_ephemeral.getPublicKey(), remote_static, remote_ephemeral, encPayload)

# Send
await sendFrame(ds, remote_static, frame)
Expand Down
2 changes: 2 additions & 0 deletions src/chat/types.nim
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Original file line number Diff line number Diff line change
@@ -1,2 +1,4 @@
type MessageId* = string
type Content* = seq[byte]

type RemoteKeyIdentifier* = uint32
13 changes: 10 additions & 3 deletions src/chat/utils.nim
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Expand Up @@ -7,9 +7,16 @@ proc getCurrentTimestamp*(): Timestamp =
result = waku_core.getNanosecondTime(getTime().toUnix())


proc hash_func*(s: string | seq[byte]): string =
# This should be Blake2s but it does not exist so substituting with Blake2b
result = getBlake2b(s, 4, "")
proc hash_func_bytes*(n: static range[1..64], s: string | seq[byte]): seq[uint8] =

let key = ""
var b: Blake2b
blake2b_init(b, n, cstring(key), len(key))
blake2b_update(b, s, len(s))
result = blake2b_final(b)

proc hash_func_str*(n: static range[1..64], s: string | seq[byte]): string =
result = $hash_func_bytes(n,s)

proc bytesToHex*[T](bytes: openarray[T], lowercase: bool = false): string =
## Convert bytes to hex string with case option
Expand Down
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